In the prior art, a cylinder uses a high-pressure gas or a high-pressure liquid as a power source to reciprocate motion for a transmission function. As shown in FIG. 1, the cylinder generally includes a cylinder body 1, a main cavity body 2, a piston 3, and a piston rod 4. The cylinder body 1 defines an air inlet and an air outlet 5 in each of two opposite ends of the cylinder. In a working process of the cylinder, the piston impacts a front cover and a back cover of the cylinder body causing the piston to stop. A stopped process of the piston impacting the cylinder causes great mechanical damage to the cylinder, and greatly increases abrasion and deformation, resulting in reduction of life of the cylinder. In addition, vibration is generated by the impact. When the cylinder transmitted workpieces, the workpieces sensitive to the vibration may be adversely affected and application range is limited.